Clutch mechanism, especially for a motor vehicle

ABSTRACT

The clutch mechanism comprises a cover plate (4), a diaphragm (5) bearing on the cover plate (4), assembly (8) applying the diaphragm (5) pivotally to the cover plate (4), and extending through the diaphragm (5) via widened apertures (53), together with at least one pressure plate (3) on which the diaphragm (5) bears by virtue of an annular projecting engagement element (31), which is divided into engagement sectors. The assembly (8) carries a support crown (71) which is coupled in rotation to the assembly (8), and which is extended in its plane and at its outer periphery by drive tongues (70) which extend through the projecting engagement element (31) of the pressure plate (3). The tongues (70) are adapted to be fixed at their free end to the pressure plate (3). In a modification, the drive tongues (70) are fixed with respect to a secondary abutment member (6, 60, 160) carried by the assembly (8).

The present invention relates to a diaphragm clutch mechanism,especially for a motor vehicle.

More particularly, the invention is concerned with a clutch mechanism ofthe type comprising a first member having a generally annular form,known as a cover plate, which is adapted to be applied on the reactionplate of the clutch, a second member of generally annular shape referredto as a diaphragm, which bears on the cover plate and which comprises aperipheral portion defining a Belleville ring together with a centralportion which is divided into radial fingers by slots for cooperationwith a clutch release bearing, assembly means extending through thediaphragm via widened apertures defined by the slots of the diaphragm inthe vicinity of the inner periphery of the Belleville ring of thediaphragm, with the said assembly means carrying a secondary abutment infacing relationship to a primary abutment which is carried by the coverplate, whereby to apply the diaphragm pivotally to the cover plate, andat least one plate, referred to as a pressure plate, which is fixed withrespect to the cover plate for rotation with the latter while beingmounted for axial movement with respect to it, and on which theperipheral portion of the diaphragm bears via an annular projectingengagement element which is divided into annular engagement sectors andwhich is formed at the outer periphery of the pressure plate for thispurpose.

Such a mechanism is described in the document EP-A-0 535 702, and in theApplication FR 2 692 637 filed on 19 Jun. 1992. In the document EP-A-0535 702, the assembly means comprise retaining lugs, which arerelatively thin and flat, being integral with the cover plate, and whichextend axially through the diaphragm and have a locating bend at theirfree end.

These assembly means also carry at least one secondary abutment memberin the form of a ring crown which provides a secondary abutment for thediaphragm, the said ring crown being interposed axially between thediaphragm and a support crown which is engaged on the retaining lugs,and which is located in one axial direction on the locating bend formedon the retaining lugs at their free end.

In the document FR 2 692 637, the assembly means comprise rivets whichpass axially through the said apertures of the diaphragm, and which alsocarry a secondary abutment member in the form of a ring crown which isinterposed axially between the diaphragm and a support crown fixed tothe rivets.

The cover plate of the mechanism does of course offer a primary abutmentin facing relationship with the secondary abutment, in such a way thatthe diaphragm is mounted pivotally between its primary and secondaryabutments, located radially inwardly of the projecting engagementelement of the pressure plate.

An object of the present invention is to make further use of thecomponents carried by the assembly means.

In accordance with the invention, a clutch mechanism of the typedescribed above is characterised in that one of the elements consistingof the secondary abutment member and the support crown is coupled inrotation to the said assembly means by mating cooperation therewith, andis extended at its outer periphery, by drive tongues which extend awayfrom its plane and are fixed with respect to the said element, and whichextend through the projecting engagement element of the pressure platevia slots separating the said engagement sectors, and in that the saidtongues are adapted to be secured at their outer end to the pressureplate, in such a way that they couple the pressure plate to the coverplate, for rotation with it but with axial mobility thereon.

In one embodiment, the assembly means carry only one secondary abutmentmember, so that it is the latter that includes the drive tonguesaccording to the invention.

Thanks to the invention, the support crown or the secondary abutmentmember provides a rotary coupling, with axial mobility, for the pressureplate with respect to the cover plate. By means of these drive tongues,it gives the pressure plate a return action.

It will be appreciated that the assembly means are retained, to thebenefit of standardisation.

As a result, the cover plate is simplified, because there is no longerany need to provide holes in the latter for fastening the tangentialtongues that conventionally provide the rotary coupling of the pressureplate to the cover plate.

The radial flange of the cover plate is accordingly stiffened.

In addition, since the drive tongues according to the invention have aroot zone which lies radially inwardly of the projecting engagementelements of the pressure plate, the result is obtained that the coverplate is indented to a lesser extent at the level of the extreme ends ofthe tongues. In this connection, the cover plate conventionally has theform of a hollow plate, and it is necessary to recess the annular skirtportion and the annular fastening flange of the latter in order topermit the tangential tongues to be accommodated. It is these tonguesthat determine the size of the slots in the cover plate.

Thanks to the invention, the size of the slots, especially in thecircumferential direction, can be reduced in such a way that the coverplate is stiffened, leading to improved lift of the pressure plateduring release of the clutch.

In one embodiment, the tongues are inclined, each of them being fixed toa projecting element formed on the pressure plate at its outerperiphery.

Thanks to the invention, this projecting element is of reduced size ascompared with conventional lugs formed on the pressure plate for thefastening of the tangential tongues.

As a result, the diametral size of the pressure plate, and therefore ofthe mechanism, is reduced, since the lugs in the prior art usuallyextend through the skirt portion of the cover plate.

In the present invention, the projecting elements do not necessarilypass through the skirt portion of the cover plate, and in all cases,components of the motor vehicle can be brought very close to the coverplate. In a second embodiment, the tongues may extend radially, beingrecessed to allow the annular engagement sectors of the pressure plateto pass.

In every case, the number of components is reduced as compared with theprior art, because the tongues are fixed with respect to the supportcrown or the secondary abutment member, the latter being preferably heattreated so as to give them the desired elasticity.

In addition, the number of fasteners required for securing the tonguesis also reduced.

Besides this, the danger of any error is reduced. In this connection, inthe prior art there was a danger of error as regards the choice oftongues, which are stored separately.

Thanks to the invention, this danger of error is eliminated, because thesupport crown or the secondary abutment member carries the tongues.

In addition, fitting of the mechanism is greatly facilitated since, byvirtue of the invention, it is possible to form a unitary sub-assemblycomprising the cover plate, with its primary and secondary abutments,together with the drive tongues carried by one of the elementsconsisting of the support crown and the secondary abutment member.

This sub-assembly may be made in one production unit and be finallyassembled with the pressure plate in another production unit, with onlyone operation being necessary for fixing the tongues.

When the assembly means consist of axial lugs, it is sufficient toprovide apertures at the inner periphery of the support crown orsecondary abutment member, for preventing rotation of the support crown.

When the assembly means comprises rivets, prevention of rotation of thesupport crown is naturally provided by the rivets.

In one embodiment it is the support crown that carries the drivetongues.

According to one feature, the support crown is treated, being forexample subjected to an operation consisting of heating followed byquenching, so as to give it the elasticity desired for its drivetongues.

The secondary abutment of the diaphragm is of course not necessarilycarried by a ring crown, but it may for example be formed in a thrustring.

In every case, the support crown constitutes a tool which absorbs theforces of bending the lugs or the force of upsetting the rivets, so thatthe secondary abutment of the diaphragm is protected.

A mechanism obtained in this way, in a simple and inexpensive manner,has excellent operating characteristics, a simplified cover plate, apressure plate which is easily made by moulding, and a support crownwhich is obtained by a simple press-forming operation.

In addition, the dynamic balancing of the clutch mechanism is improved.

It is of course possible to reverse the structures, in such a way thatthe secondary abutment member can carry the drive tongues. In amodification, and in the manner mentioned above, the support crown maybe omitted, and it is then the secondary abutment member that carriesthe drive tongues.

In all cases the secondary abutment member, or the support crown,includes an endless annular portion.

After being fitted into the mechanism, the tongues are inclined into theaxial direction, and urge the pressure plate towards the cover plate.

Further advantages will appear in the light of the followingdescription, of the attached drawings, in which:

FIG. 1 is a view in axial cross section of a clutch module equipped witha support crown in accordance with the invention;

FIG. 2 is a view in the direction of the arrow 2 in FIG. 1, showing thesupport crown with its associated pressure plate;

FIGS. 3 and 4 are views similar to FIGS. 1 and 2, but for anotherembodiment;

FIGS. 5 and 6 are views similar to FIGS. 1 and 2, for yet anotherembodiment;

FIG. 7 repeats part of FIG. 5 on a larger scale.

The drawings show a clutch module for a motor vehicle, constituting aunitary assembly and comprising, in axial succession, a unitary assembly1 referred to as a clutch mechanism, a clutch friction wheel 2, and areaction plate 10, also referred to as a flywheel.

The clutch mechanism 1, which in the present case is of thepush-to-release type, comprises all assembly of annular components,namely a cover plate 4, a diaphragm 5 and a pressure plate 3. The coverplate and the diaphragm together constitute a unitary assembly, thediaphragm being mounted pivotally between a primary abutment 41, carriedby the cover plate 4, and a secondary abutment, which is carried byassembly means 8 in a manner to be described below.

The clutch friction wheel 2 comprises a friction disc 21 which carries,fixed to each of its faces, a friction liner 22, which may be dividedinto friction pads.

The said disc 21 is coupled, in this example through circumferentiallyacting springs 23 together with axially acting friction means, to a hub30 which is splined internally. For this purpose, the disc 21 isfastened to two guide rings 25, which are arranged on either side of ahub plate 27 which is fixed to the hub 30, in this example by seaming.

More precisely, the disc 21 in this example is backed on to one of theguide rings 25, and is fastened to these latter by means of spacers 26which extend through the hub plate 27 with a circumferential clearance,so as to secure the two guide rings 25 together. The springs 23, whichin this example are in the form of coil springs, or in a modifiedembodiment blocks of elastic material such as blocks of elastomer, aremounted in windows formed in mutually facing relationship in the hubplate 27 and the rings 25, respectively.

The said friction means comprise a bearing 24 which is interposedaxially between one of the rings 25 and the hub plate 30, together witha thrust ring 28 and an axially acting resilient ring 29, which in thisexample is of the Belleville ring type, interposed between the hub plate27 and the other ring 25.

The ring 29 bears on the appropriate ring 25 so as to act on the thrustring 28, which is mounted on the said ring 25 for rotation with it inthis example, in a manner known per se by means of spigots, and forgripping the bearing 24 between the hub plate 27 and the other ring 25.

The bearing 24, which in this example is of plastics material, isprovided with recesses in which are fixed the heads of fastening studs12 which fasten the clutch module to the crankshaft of the internalcombustion engine of the vehicle, in the manner described in thedocument FR 93 11325, filed on 23 Sep. 1993.

These studs 12 are adapted so that their threaded portion extendsthrough the reaction plate 10, so as to fasten the clutch module to thecrankshaft.

Thus in FIG. 1, the position of the studs before the module is fittedinto the vehicle can be seen in the lower part of the Figure, while theupper part of the said Figure shows the position of the studs 12 afterthe module has been fitted in the vehicle.

The hub plate 27 is of course formed with holes through which tools fortightening the studs 12 can pass.

This module accordingly forms a unitary assembly which is dynamicallybalanced, and which is secured on the crankshaft.

To this end, the cover plate 4 of the mechanism 1 is placed against thereaction plate 10 carrying the starter crown 11. In this example,fastening is obtained by means of screws 43 extending into passagesformed in a radial fastening flange of the cover plate 4, which in thisexample is in the form of a hollow plate with a generally axiallyorientated annular skirt portion, which joins the said radial flange toa transversely orientated base portion that has a central hole.

In a modification, the fastening of the cover plate 4, and therefore ofthe mechanism 1, on the plate 10 is obtained with the use of rivets, orby seaming (FIG. 3) or otherwise.

The diaphragm 5 is mounted pivotally on the cover plate 4 by theassembly means 8 referred to above, which attach the cover platepivotally to the diaphragm.

In a manner known per se, the said diaphragm 5, annular in form,comprises a peripheral portion 51 defining a Belleville ring, and acentral portion divided into radial fingers 52 by slots which arewidened at the level of the inner periphery of the Belleville ring 51,so as to define widened apertures 53 through which the assembly means 8extend axially.

These assembly means 8 carry a secondary abutment in facing relationshipwith a primary abutment 41 carried by the cover plate 4. The secondaryabutment is carried by a secondary abutment member 6 to be describedbelow.

The diaphragm 5 is thus mounted for pivoting movement between theprimary and secondary abutments.

When the clutch is engaged, the diaphragm 5 bears in the known way onthe cover plate 4, and more precisely on the primary abutment 41, so asto urge the pressure plate 3 towards the reaction plate 10 and so togrip the friction liners 22 between the two plates 3, 10.

The torque is thus transmitted from the engine to the input shaft of thegearbox via the friction liners 22 and the internally splined hub 30, soas to couple it in rotation with the said input shaft.

In order to disengage the clutch it is necessary to exert a thrust, bymeans of a clutch release bearing (not shown), on the inner end of thefingers 52 of the diaphragm, so as to cause the latter to pivot and toremove the force exerted by the diaphragm on the pressure plate 3.

The friction liners 22 are thus disengaged. For this purpose, thediaphragm 5 bears, through the outer peripheral part of its Bellevillering 51, on a projecting annular engagement element 31 which is dividedinto annular engagement sectors, and which is formed on the pressureplate 3 at its outer periphery.

The diaphragm 5 bears, through the inner peripheral part of itsBelleville ring 51, on the primary abutment 41 when the clutch isengaged, and on the secondary abutment 6 when the clutch is caused toshift from its clutch engaged position to its clutch released position.

In this example, the assembly means 8 comprise, as in the documentEP-A-0 535 702, flat, thin lugs 42, orientated axially and projectingintegrally from the cover plate 4 (from the inner periphery of the baseportion of the latter), the said lugs 42 extending axially through thediaphragm 5 via the apertures 53 in the latter.

The primary abutment 41 is defined by a pressed-in portion formed in thebase portion of the cover plate. In a modification, it may consist of aring carried by the cover plate 4.

The secondary abutment is defined by a ring crown 6 which is ofgenerally frusto-conical form, the outer periphery of which is roundedso as to define a secondary abutment in facing relationship with theprimary abutment 41. In a modification, the outer periphery of the crown6 has a V-shaped cross section to define the secondary abutment.

This crown 6 is engaged on the lugs 42 through its inner periphery andwith a radial clearance, and constitutes a secondary abutment memberbecause it is this component that carries the secondary abutment.

A support crown 71 is also engaged on the lugs 42, with the said ringcrown 6 being interposed axially between the diaphragm 5 and the supportcrown 71, which is carried by the assembly means 8 like the crown 6.

In a manner known per se, in order to assemble the components together,the free end of the lugs 42 is bent radially away from the axis of theassembly so as to form a locating bend on which the support crown 71bears axially. This crown is thus located axially, in one axialdirection on the bend and in the other axial direction on the ring crown6, the diaphragm 5 being gripped elastically between the ring crown 6and the primary abutment 41, with a predetermined load and without anyrisk of jamming, because the support crown 71 constitutes, in a sense, atool which absorbs the force of bending the free end of the lugs 42.

In order to engage and disengage the clutch in the way described above,and the driving of the pressure plate 3 in rotation, it is accordinglynecessary that the pressure plate 3 should be coupled to the cover plate4 for rotation with it but with axial mobility.

The invention proposes to make a novel use of one of the elementsconsisting of the support crown 71 and the secondary abutment member 6.

Thus, in accordance with the invention, a mechanism of the typedescribed above is characterised in that one of the elements consistingof the support crown 71 and the secondary abutment member 6 is coupledin rotation, by mating cooperation, to the said assembly means 8, and isextended by carrying at its outer periphery drive tongues 70 whichextend away from its plane, being fixed with respect to the said elementand extending through the projecting engagement element 31 via slots 35which separate each of its annular engagement sectors from the next, andin that the said tongues are adapted to be fixed at their free end tothe pressure plate 3, in such a way that they couple the pressure plate3 to the cover plate 4 for rotation with it but with axial mobility.

The said tongues 70 are bent (FIGS. 1, 3, 5), in such a way that theyurge the pressure plate 3 towards the cover plate during the operationof releasing the clutch.

In FIG. 1, the tongues 70 are integral with the support crown 71, andare inclined in the axial and transverse directions. These tonguesextend generally tangentially with respect to the outer periphery of thesupport crown 71. The tongues 70 are accordingly resiliently deformable,and enable the pressure plate 3 to be urged towards the base portion ofthe cover plate 4.

The circumferential ends of the annular engagement sectors 31 areprofiled and inclined, as can be seen for example at 34 in FIG. 2, so asto enable the tongues 70 to pass. As can be seen in this FIG. 2, thecircumferential ends of the engagement sectors 31 are tapered, with eachdrive tongue 70 being joined to the outer periphery of the support crown71 through a root zone 73. This root zone reduces in width going towardsthe centre of the crown 71.

The crown 71 has notches 72 formed in its inner periphery and engaged ina complementary manner on the axially orientated, relatively thin andflat lugs 42 before the latter are bent over.

In this way, a simple mating rotary coupling is obtained between thelugs 42 and the crown 71. In this example this coupling is of the tenonand mortice type. In a modification, the crown 71 could be extendedtowards the axis of the assembly, in order to define closed passageshaving a rectangular cross section and adapted to be engaged on the lugs42 before the latter are bent over.

In this example, there are three tongues 70 and three sectors 31, spacedapart circumferentially at regular intervals. This number does of coursedepend on the application. In the present example nine notches 72 areprovided, the number of these being dependent on the number of the lugs42.

It will be noted that the greater part of the root zones 73 lies betweentwo notches 72.

The pressure plate 3, which is made of a mouldable material, and whichis a casting in this example, has at its outer periphery three radiallyprojecting elements 32 that match the shape of the free ends of thedrive tongues 70, being formed with holes at their free ends foraccommodating fastening members 33, which in this example are pinshaving a head engaged on the tongues 70, and a shank which isforce-fitted into a hole formed in the projecting element 32, which inthis example is generally semicircular in shape, of the pressure plate3.

Preferably, and in a known manner, the pins 33 are knurled for thispurpose. Fastening of the pins 33 can of course be obtained by adhesivebonding or otherwise, and in a modification, these pins 33 may bereplaced by rivets (FIG. 7), or any other fastening member such asbolts.

The support crown 71 is preferably heat treated so as to give thetongues 70 the desired elasticity.

In this connection, a heating operation, following by quenching, ispreferably carried out.

As will be understood, the crown 71, which in this example is of metal,is obtained with its tongues 70 readily by a press-forming operation,and it is possible to form a sub-assembly, consisting of the cover plateand support crown, which can finally be attached on to the pressureplate 3 by means of the pins 33.

As will appear from FIG. 2, the projecting elements 32 have a smallradial dimension, so as to reduce the radial size of the clutchmechanism 1. Dynamic balancing of the mechanism is also facilitated.

It will also be noted that the slots formed in the radial flange portionof the cover plate 4 and in the axially orientated skirt portion of thelatter are of reduced dimensions, especially in the circumferentialdirection, as compared with those in the prior art, the said slots beingmatched to the size of the projecting elements 32 so that the coverplate is stiffened.

Thus, FIG. 2 shows in two lines at 90 the limits of the said slot. Thisslot in the radial flange portion of the cover plate is necessary inorder to enable the tool used for fastening the pins 33 to the pressureplate 3 to pass through.

The present invention is of course not limited to the embodimentdescribed, and in particular the tongues 70 may extend radially.

For example, in FIG. 2 the tongues may extend in the radial directionthrough a slot 35. These tongues are then triangular in shape, so as tohave a free end which enables the pressure plate 3 to be fastened bymeans of the pins 33. These tongues are therefore resiliently deformableby virtue of their triangular configuration, and preferably, as in FIGS.1 and 2, the support crown 71 is heat treated so as to give the tonguesthe required elasticity.

The pressure plate 3 also carries at its outer periphery projectingelements for the fastening of the pointed free ends of the radialtongues. These projecting elements match the shape of the said free end,having a hole for passage of the fastening pins 33 or of any otherfastening member, such as rivets, bolts or the like.

It is of course possible to increase the number of annular engagementsectors 31, and in that case to increase the width of the radialtongues, with the latter then having a central slot through which anannular sector 31 extends. In this case, the tongues lie in twoconsecutive slots 35.

The assembly means may of course consist, as described in the documentFR 92 07514, of rivets secured to the cover plate and enabling thesupport crown 71 to be fastened by seaming. In this case, the supportcrown 71 is located axially in both directions by the assembly means 8,whereas in FIG. 1 the said crown was located axially in only onedirection by the said assembly means 8.

In this case, the crown 71 is extended towards the axis of the assembly,in order to define holes through which the rivets pass before thesupport crown 71 is riveted.

In this case the ring crown 6 is inclined in the opposite direction fromthat in FIG. 1. This ring crown 6 bears at its outer periphery on thesupport crown and at its inner periphery on the diaphragm 5.

Any other assembly means may be envisaged, and for example theseassembly means may consist of a plurality of comb-shaped annularsectors, engaging on the outer face of the base portion of the coverplate through their annular portion joining together the teeth of thecomb, with the said teeth passing through the apertures 53 in thediaphragm so as to be bent radially outwardly into contact with thesupport crown 71.

The ring crown 6 may be replaced by a ring having the secondary abutmentand constituting the secondary abutment member.

It is of course possible to reverse the structures as shown in FIGS. 3and 4, in which those elements common to FIGS. 1 and 2 are given thesame reference numerals.

Thus, in FIGS. 3 and 4, it is the secondary abutment member 60 thatcarries integrally the drive tongues 70, which are inclined in the axialand transverse directions. Each of these tongues has a free end throughwhich the fastening pins 33 are engaged, these being engaged in a blindhole formed in the projecting elements 132 of the pressure plate.

These radial projecting elements 132 are modified as compared with thosein FIGS. 1 and 2, and in the present example they are in the form ofsemicircular ears which project from the outer periphery of the plate 3.

The ring crown 60 has a continuous circular crown portion 61 which hasinternal notches 62 identical with the notches 72 in FIG. 2, for fittingon the lugs of the assembly means 8 and for coupling in rotation withthe latter by mating cooperation.

This crown portion is rounded at 63 in its outer periphery, so as todefine the secondary abutment which is interrupted by the tongues 70.The tongues 70 are joined to the crown portion 60 through a root zone173 which is inclined to a lesser extent than in FIG. 2.

These root zones 73 are located in the slots 35 which separate twoannular engagement sectors 31 of the pressure plate 3.

It will be noted that the cover plate 4 is attached on the reactionplate 10 by seaming, the said cover plate being extended at the outerperiphery of its axial fastening flange by an axially orientated annularextension, which is deformed so as to be engaged in a groove of thereaction plate or flywheel.

In a modification (FIGS. 5 to 7), the assembly means may consist ofrivets 142 which are secured to the base portion of the cover plate 4,for fastening the secondary abutment member 160.

In this Figure, no support crown is provided, and the engagement member160 is fastened by seaming to the rivets 142 that extend through thediaphragm 5 via the apertures 53.

The abutment member 160 has a crown portion 161, which is formed withholes 162 from place to place for fastening it by seaming to the rivets142. This crown member has a toroidal secondary abutment 163 at itsouter periphery.

This abutment is interrupted by the root zones 273 of the tongues 70joining them to the crown portion 161. As can be seen in FIG. 6, a slot164 separates the secondary abutment 163 from the root zone 273.

The tongues 70 are secured by means of rivets 133 to the projectingelements 132, which are in the form of a half moon, of the pressureplate 3.

In a modification, the support crown 71 can be omitted in FIG. 3, sothat the ring crown is mounted on the assembly means 8 as in thedocument U.S. Pat. No. 4,751,991. This crown portion then carries thedrive tongues as in FIG. 3.

The clutch mechanism may of course not necessarily be part of a module,and it may be attached on a reaction plate which is fitted in advance onthe crankshaft of the engine, for example by means of a threadedconnection.

Similarly, the clutch friction wheel 2 may be of the rigid type, withits disc 21 being fastened directly on the hub plate 27, which may beintegral with the hub 30.

The clutch may have a plurality of pressure plates. The diaphragm 5 may,instead of being mounted inside the cover plate 4, that is to say on thesame side as that surface of the cover plate that faces towards thepressure plate 3 as in FIGS. 1 and 2, be mounted outside the coverplate, with the pressure plate then extending through the base portionof the cover plate by its annular engagement sectors.

In that case, the pressure plate may have axially orientated projectingelements passing through the cover plate and enabling the tangentialtongues to be fastened.

Finally, the drive tongues 70 may be made of plastics material, eitherreinforced or not, being moulded on to the support crown 71 or on to thesecondary abutment member 6, 60.

In all cases, the drive tongues (70) are fixed to the element consistingof the support crown 71 or the secondary abutment member 6, 60 as thecase may be, so that their root portions are in the plane of the latter,and so that no fastening member is present that could hinder themovement of the pressure plate 3.

We claim:
 1. A clutch mechanism, comprising a cover plate (4), adaptedto be attached on the reaction plate (10) of a clutch, a diaphragm (5)bearing on the cover plate (4) and comprising a peripheral portion (51)which defines a Belleville ring together with a central portion dividedinto radial fingers (52) by slots for cooperation with a clutch releasebearing, assembly means (8) applying the diaphragm (5) pivotally to thecover plate (4) and extending through the diaphragm (5) via widenedapertures (53) formed in the diaphragm (5) in the region of the innerperiphery of its Belleville ring (51), and at least one pressure plate(3), which is secured to the cover plate (4) for rotation with the coverplate while being mounted for axial movement with respect to the coverplate, and on which the peripheral portion (51) of the diaphragm (5)bears by virtue of an annular projecting engagement portion (31), whichis divided into engagement sectors and which is disposed for thispurpose at the outer periphery of the pressure plate (3), wherein,firstly, a support crown (71) is located in at least one axial directionon the assembly means (8), and secondly, a secondary abutment member (6,60, 160) is interposed axially between the diaphragm (5) and the supportcrown (71), the cover plate (4) carrying a primary abutment (41) infacing relationship with a secondary abutment carried by the secondaryabutment member (6, 60, 160), with the diaphragm (5) being interposedbetween the abutments, characterized in that one of the elementsconsisting of the support crown (71) and the secondary abutment member(6, 60, 160) is coupled in rotation to the assembly means (8) by matingcooperation therewith, and is extended at its outer periphery, by drivetongues (70) which extend away from its plane and are fixed with respectto the element, and which extend through the projecting engagementportion (31) of the pressure plate (3) via slots (35) separating theengagement sectors, and in that the tongues (70) are adapted to besecured at their outer end to the pressure plate (3), in such a way thatthe tongues couple the pressure plate (3) to the cover plate (4), forrotation with the cover plate but with axial mobility thereon.
 2. Aclutch mechanism, comprising a cover plate (4), adapted to be attachedon the reaction plate (10) of a clutch, a diaphragm (5) bearing on thecover plate (4) and comprising a peripheral portion (51) which defines aBelleville ring together with a central portion divided into radialfingers (52) by slots for cooperation with a clutch release bearing,assembly means (8) applying the diaphragm (5) pivotally to the coverplate (4) and apertures (53) formed in the diaphragm (5) in the regionof the inner periphery of its Belleville ring (51), and at least onepressure plate (3), which is secured to the cover plate (4) for rotationwith the cover plate while being mounted for axial movement with respectto the cover plate, and on which the peripheral portion (51) of thediaphragm (5) bears by virtue of an annular projecting engagementportion (31), which is divided into engagement sectors and which isdisposed for this purpose at the outer periphery of the pressure plate(3), wherein said assembly means (8) carry a secondary abutment member(6, 60, 160), said cover plate (4) carrying a primary abutment (41) infacing relationship with a secondary abutment carried by the secondaryabutment member, with the diaphragm (5) being interposed between saidabutments, characterized in that the secondary abutment member (6, 60,160) is coupled in rotation to said assembly means (8) by matingcooperation therewith, and is extended, in its plane and at its outerperiphery, by drive tongues (70) which are fixed to said secondaryabutment member, and which extend through the projecting engagementportion (31) of the pressure plate (3) via slots (35) separating saidengagement sectors, and in that said tongues (70) are adapted to besecured at their outer end to the pressure plate (3), in such a way thatsaid tongues couple the pressure plate (3) to the cover plate (4), forrotation with the cover plate and with axial mobility thereon.
 3. Amechanism according to claim 1, wherein the drive tongues (70) areinclined, and extend generally tangentially with respect to the element,consisting of the support crown (71) or secondary abutment member (6,60), with respect to which said tongues are fixed.
 4. A mechanismaccording to claim 3, wherein each drive tongue (70) is joined to itselement consisting of the support crown (71) or secondary abutmentmember (6, 60), with respect to which it is fixed, through a root zone(73, 173) which reduces in width towards the centre of the support crown(71).
 5. A mechanism according to claim 1, wherein one of the elementsconsisting of the support crown (70) and the secondary abutment member(6, 60, 160), with respect to which the tongues are fixed, has at itsinner periphery notches (72) which are engaged, in a complementarymanner, on lugs (42) which are orientated axially, being relatively thinand flat, and which are part of the assembly means (8).
 6. A mechanismaccording to claim 1, wherein the circumferential ends of the annularengagement sectors (31) of the pressure plate (3) are profiled andinclined, to enable the drive tongues (70) to pass.